1. Field of the Invention
The present invention relates to platform lifting mechanisms, and more particularly, to an improved mechanism for efficiently utilizing the hydraulic force while maintaining its safety.
2. Description of the Related Art
A number of mechanisms have been designed in the past that incorporate a scissor-type assembly equipped with hydraulic cylinders for distending its members. Ideally, in its lowermost position, the cylinders will be as flat as possible, parallel to the plane of the chassis where these mechanisms are usually mounted. An in distension, the criss-crossed structural members extend towards a vertical position to fully utilize the capabilities of the hydraulic cylinders. These lifting mechanisms usually carry variable loads and their hydraulic cylinders can snap out of their positions. This has caused fatalities in the industry.
Applicant believes that the closest reference corresponds to U.S. Pat. No. 3,891,108 issued to Charles Traficant. However, it differs from the present invention because it lacks the safety features claimed below that prevents the hydraulic cylinders from snapping out when load conditions changes. Traficant discloses abutment 82 to limit the travel of piston rod 55 and roller assembly 56; 58; 60 and 62 in one direction but there is nothing to prevent it from slipping out in the other direction. When load conditions are reduced drastically, the hydraulic means continue to push upwardly and cause piston rod to continue its angularly upward travel.
Other patents describing the closest subject matter provide for a number of more or less complicated features that fail to solve the problem in an efficient and economical way. None of these patents suggest the novel features of the present invention.